… is from the late Jim Buchanan’s 1963 Presidential address to the Southern Economic Association – a pioneering address entitled “What Should Economists Do? “; this quotation is from page 38 of the version that appears in volume 1 of The Collected Works of James M. Buchanan: The Logical Foundations of Constitutional Liberty  (original emphasis):
The “market” or market organization is not a means toward the accomplishment of anything. It is, indeed, the institutional embodiment of the voluntary exchange processes that are entered into by individuals in their several capacities. This is all that there is to it. Individuals are observed to cooperate with one another, to reach agreements, to trade. The network of relationships that emerges or evolves out of this trading process, the institutional framework, is called “the market.” It is a setting, an arena, in which we, as economists, as theorists (as “onlookers”), observe men attempting to accomplish their own purposes, whatever these may be…. In this conception, there is no explicit meaning of the term “efficiency” as applied to aggregative or composite results. It is contradictory to talk of the market as achieving “national goals,” efficiently or inefficiently.